It is well known that many medical complications are caused by the partial or total blockage of a blood vessel in a patient. Depending on the location of the particular blockage or stenosis, the patient can experience cardiac arrest, stroke, or necrosis of tissues or organs. Commonly, the stenosis results from plaque build-up in an artery. The plaque can vary in size and shape and can develop in different locations in a particular patient's cardiovascular system.
Several procedures have been developed to treat stenosis in the vessels of patients. For example, procedures such as angioplasty, stenting, incising and dilating, and atherectomy have been developed to treat stenosis in vessels. However, none of these procedures have been entirely successful in inhibiting or preventing the re-stenosis of a vessel after the procedure has been completed.
Recent studies have demonstrated the efficacy of radiation for inhibiting or preventing re-stenosis in a vessel by inhibiting or preventing the growth of fibrotic cells in the vessel wall, commonly referred to as neointima. In fact, devices have been developed for performing endovascular radiotherapy on a treatment site of a vessel to inhibit or prevent re-stenosis in the vessel. These devices commonly use a catheter to position a right, circular cylinder shaped radioactive segment in a vessel lumen of the vessel. The radioactive segment emits radiation until a prescribed dose of radiation has been delivered. However, the radioactive segment used with these devices has not been entirely satisfactory. For example, the radioactive segment has been unable to emit adequate amounts of radiation within the necessary short treatment times. Thus, it is often necessary to leave the radioactive segment in the vessel for an extended period of time in order to deliver a prescribed dose of radiation.
One attempt to solve this problem includes enlarging the diameter of the radioactive segment. This decreases the distance between the surface of the radioactive segment and the treatment area of the vessel, thus increasing the dose rate to the treatment area. However, enlarging the diameter of the radioactive segment limits these devices to relatively large and straight vessels. Furthermore, the enlarged diameter of the radioactive segment reduces blood flow in the vessel during treatment. This may cause potentially lethal complications.
An additional shortcoming of existing devices is the inflexibility of the right, circular cylinder shaped radioactive segment. In many instances, this inflexibility precludes treatment in small vessels and vessels having relatively sharp corners.
Further, existing devices include a radioactive segment which is typically made of a variety of different radioactive materials. However, these radioactive materials often emit complex and sometimes undesirable "contaminant radiation," thereby reducing the effectiveness of these radioactive materials. Accordingly, the radioactive segment is required to be encapsulated in another material to ensure that the radioactive contaminants are not released from the radioactive segment. This can add size and inflexibility to the radioactive segment. Furthermore, it also adds complexity to the design of the device and increases the cost of manufacturing the device. Moreover, many of these radioactive segments require excessively long activation times in the reactor to achieve suitable activity levels required for acceptable dose rates. Because of the low dose rates of the radioactive segments, excessively long treatment times are often necessary.
In light of the above, it is an object of the present invention to provide a device and method for quickly delivering a precise dose of radiation to a treatment site of a vessel. It is another object of the present invention to provide a device and method for delivering a dose of radiation to a treatment site of a relatively small and/or curved vessel. Still another object of the present invention is to provide a radiation source which is substantially disposable and is relatively inexpensive. Still another object of the present invention is to provide a device which is relatively safe and easy to manufacture and/or assemble. Yet another object of the present invention is to provide a radiation source that may be used without encapsulating or coating, may be used in an open ended catheter and may directly contact the patient's blood. Still another object of the present invention is to provide a way to quickly and accurately position the radiation source within the patient.